Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	May 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 50,000	$ 45,106			$ 0
Operating lease liability	52,800	46,940
Derecognition of deferred rent	2,800
Derecognition of build-to-suit lease	9,900	$ 9,886	$ 0
Derecognition of lease financing obligation	10,500
Cumulative effect adjustment from adoption of ASC 842	556
Convertible senior notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest rate		0.75%		0.75%
Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment from adoption of ASC 842	$ 556